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Basic operators:
A few terms: data objects, lvalues, rvalues, and operators
The purpose of an assignment expression statement is to store a value in a memory location. The data stores used to store values are collectively called data objects, and the C standard only uses the term object when referring to this concept.
There are several ways to identify objects: using variable names, specifying elements of arrays, members of structures, using pointer expressions (the pointer stores the address of the object it points to)
An lvalue is a C language term used to identify a name or expression of a specific data object. Objects refer to the actual data storage, while lvalues are labels used to identify or locate the storage location.
A new term has been added to the C standard: modifiable lvalue, which is used to identify a modifiable object. So, the left side of an assignment operator should be a modifiable lvalue, better to use the term "object-located value".
An rvalue is a quantity that can be assigned to a modifiable lvalue and is not itself an lvalue.
C uses operators to represent arithmetic operations, and the operand is the object that the operator operates on.
Assignment operator: =
In C language, the assignment operator is "="
a = 2; // assign value 2 to variable a
The left side of "=" is a variable name, and the right side is the value assigned to the variable
Addition operator: +
The addition operator is used for addition operations to add the values on both sides of it
a = 1 + 1;
The added value can be a variable or a constant
int a = 1; int b = 3; c = a + b;
Minus operator:-
The minus operator is used for subtraction, subtracting the number on the left from the number on the right
a = 3 - 1;
Addition operator + and subtraction operator - are known as binary operators i.e. these operators require two operands to complete
Symbolic operators: - and +
The minus sign can also be used to identify or change the algebraic sign of a value
a = -1; b = -a;
The plus sign does not change the value or sign of the operand
a = +1;
The plus and minus signs used in this way are called unary operators, i.e. only one operand is required
Multiplication operator: *
The symbol * means multiplication
a = 1 * 3;
Division operator: /
The symbol / means division, the value on the left of the / is the dividend, and the value on the right of the / is the divisor
The result of floating point division is a floating point number, the result of integer division is an integer, and an integer is a number without a fractional part.
In C, the fractional part of the result of integer division is discarded, a process called truncation
Integer division truncates the fractional part of the calculation result and does not round the result
The result of mixed integer and floating point calculations is a floating point number
In fact, the computer can't really divide a floating point number by an integer, the compiler will convert both operands to the same type, and the integer will be converted to a floating point number
#include <stdio.h>
int main(void)
{
printf("integer division: 5/4 is %d \n", 5 / 4);
printf("integer division: 6/3 is %d \n", 6 / 3);
printf("floating division 5./4. is %1.2f \n", 5. / 4.);
printf("mixed division 5./4 is %1.2f \n", 5. / 4);
return 0;
}
operation result
For integer division of negative numbers, the method to deal with the fractional part is to truncate towards zero, that is, to directly discard the fractional part
-3.8 performs zero-trend truncation to convert to -3